Ben Roethlisberger’s injury is expected to keep the Pittsburgh Steelers quarterback out for quite some time, a source close to the team is now saying.

Roethlisberger was injured on a sack against the Kansas City Chiefs on Monday Night Football, an injury that Steelers head coach Mike Tomlin described as a shoulder sprain.

But Ben Roethlisberger also suffered a rib injury on the same play, a source told ESPN. The source added that it is unknown how long the injury will keep the quarterback out, while another source with the Steelers said the team is preparing to move ahead with backup Byron Leftwich as the starter until Roethlisberger can return.

“It doesn’t look like you’re going to have Ben this week,” the source told ESPN of Ben Roethlisberger’s injury. “We’re looking at next week as a possibility as of right now.”

The severity of the Ben Roethlisberger injury was evident during the game itself, Yahoo! Sports noted. The team took the unusual step of sending him directly to the hospital for an MRI, and a source characterized the injury as “unusual.”

Making the Ben Roethlisberger injury even more harmful to the Steelers is the fact that the team is right in the middle of a playoff race. Pittsburgh sits a game back of Baltimore for the lead in the AFC North, and currently occupies the final Wild Card playoff spot. The team has been able to play well without Roethlisberger in the past, going 3-1 at the beginning of 2010 when Big Ben was suspended.